Furnace slot seal



Jan. 14, 1958 E. w. DANY 2,819,389

FURNACE SLOT SEAL Filed Feb. 26, 1954 2 Sheets-Sheet 1 INVENTOR. flM'E W DAN) Jan. 14, 1958 E, w. DANY FURNACE SLOT SEAL 2 Sheets-Shqet '2 Filed Feb. 26, 1954 INVENTOR. [(11462 M. DAN) ,1 Arron/ans FURNACE SLOT SEAL Elmer W. Dany, Brecksville, Ohio, assignor to Ferro Corporation, Cleveland, Ohio, a corporation of Ohio Application February 26, 1954, Serial No. 412,851

4 Claims. (Cl. 2638 The invention, relating to furnace construction, is more particularly concerned with an improved seal for the slot generally provided in the roof of an enameling or other similar type furnace to permit the work to be supported iii the furnace chamber by means of externally mounted drop rods extending through the slot.

The usual construction of an enameling furnace includes an overhead track from which the ware-supporting drop rods are suspended and a chain type conveyor for maintaining the rods in spaced relation and moving the same along the slot. some form of seal must be provided for such slot to prevent particles of dirt, scale and the like from falling therethrough and onto the ware being burned in the furnace chamber, the presence of such foreign matter on the ware surfaces obviously resulting in the production of defective articles. Various forms of sliding seals have been proposed heretofore, and the most successful of these has been an assembly of articulated shoe plates carried by thesever'al drop rods in overlapped relation and adapted to engage slidably with shoe tracks located at the upper sides of the slot. However, a certain amount of dust does collect on the shoe plates and this is agitated by the plate movement. Additionally, the plates in time begin to deteriorate due to repeated subjection to the furnace heat and thus must be repaired or replaced when this occurs to prevent the plates themselves from dropping particles on the ware.

It is among the objects of my invention to provide an inexpensive and efiicient seal for such a furnace slot without the use of shoe plates or other like mechanical elements bridging the slot. A further object is to seal a furnace slot by means of a flowing air curtain traversing the outer end of the slot at high velocity, whereby falling particles of dirt, scale and the like are unable to pass therethrough. It is also an object to provide an air seal of this nature which may be continuous over the entire extent of the slot thereby to eliminate completely any mechanical engagement between the drop rods and the furnace. Other objects and advantages of the invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention maybe employed.

;In said annexed drawings; p

Fig. l is a top plan view of an air circulating duct systern effective to seal the roof slot of a furnace;

Fig. 2 is an end view showing the-circulative system of Fig. l as used with a slotted furnacer'oof; and Fig. 3 is a vertical section on an enlarged scale 'of a slightly modified form of the invention.

Referring now to the drawings in detail, the duct'ar- It has long been recognized that rangement shown in Figs. 1 and 2 is designed to produce a relatively thin and narrow air curtain of considerable length for sealing a straight section of an enameling furnace roof slot. Thisarrangement comprises both supply and recovery systems, designated generally at A and B, respectively, with air impelling means in the form of a fan 10 and an electric drive motor 11 positioned operatively between the two to feed air under pressure to the supply system and recirculate the air recovered.

Connected to the fan outlet is a distribution box 12 which divides the flow between the two similar supply headers 13 extending from opposite sides of the box. Each header 13 has a plurality of branched lines 14, three being shown, leading therefrom at uniformly spaced points with the header diameter being correspondingly reduced at such points. The branch lines connect respectively with a series of secondary supply headers '15 arranged to form a row of the same. Leading from each secondary header are four parallel feed lines 16 connected at their other ends with a discharge pipe 17 disposed generally parallel to the associated secondary header so that the several such discharge pipes likewise form a row. As shown, the discharge pipes 17 are closely spaced end-toend, and each has a slot 13 in the outer side portion thereof to form an elongated blast orifice. For expedience of manufacture, the lengths of pipe 17, which are of the same diameter, are preferably milled end-to-end to form the relatively narrow slots therein and the ends are thereafter plugged. These slots, therefore, extend substantially the entire length of the respective pipes.

It will be apparent that the air fed under pressure by the fan to the supply system just described will be distributed to the several pipes 1'7 and discharged from the latter in a series of thin air streams of appreciable width. Because of the close spacing of the several pipes 17, the individual streams of air issuing therefrom quickly combine to form a continuous air curtain extending the overall length of the several pipes. .Slide dampers 19 are provided in the branch lines 14 so that the flow of supply air to each discharge pipe may be individually regulated.

The recovery system B is generally similar structurally to the supply system and comprises a plurality of individual recovery pipes 20 respectively arranged in opposition to the discharge pipes 17. These recovery pipes are of slightly larger diameter than the discharge pipes and each has a slot 21 in its side facing the respectively associated pipe 17. Slots 21 are preferably formed in the same manner as the discharge slots 18, but are .of slightly greater size to recover most of the air flowing between the two. To assist in such recovery, a thin bafile plate 22 is welded to the top of each recovery pipe 20 to project outwardly therefrom toward the associated discharge pipe.

The plural recovery pipes are also arranged end-toend in closely spaced relation to form a row parallel to and spaced laterally from the row of discharge pipes. Each recovery pipe is connected by four return linesiltla to a parallel secondary return duct or header 23, and the latter are connected in turn by pipes 24 to the main .return header 25. Slide dampers 26 are provided in the pipes 24 for regulating the fiow of air in each. The return header 25 collects the air recovered by the plural pipes 20 and feeds the same back to the fan 10 through a return box 27 and a feed back connection 28. The return box is also provided with a fresh air inlet 29 in which a damper 30 is adjustably operative to regulate the amount of ambient air taken in. Thus the major portion of the air is recirculated through the complete system with ad ditional ambient air being supplied in amounts necessary to compensate for the air lost.

With reference now particularly to Fig. 2, the furnace with which this air circulating system is used is 0011 Patented Jan. 14, was

ventional, and, therefore, only the roof has been illustrated to show the manner in which the air curtain forms the slot seal. This roof is comprised of a plurality of refractory blocks or tiles 31 suspended by arch brackets 32 which are, in turn, secured to overhead transverse beams, one of which is shown at 33, by means of the channel member 34, all as in the usual construction of an enameling furnace. The roof is, of course, slotted at 35 and slot castings 36 are used to face the upper edge areas of the slot.

The overhead track shown at T is an I-beam suitably secured to the overhead transverse beams to extend along the furnace roof above the slot. The drop rods for supporting the ware in the furnace chamber and the conveyor for moving such rods are likewise conventional, each such rod 37 being suspended by hangers 38 having wheels 39 which ride on the lower flanges of the I-beam track. It will be understood that the construction includes several such rods maintained in spaced relation and moved along the slot by a suitably driven chain, a portion of which is indicated at 40.

In equipping the furnace with the air seal, the several discharge pipes 17 are attached to the roof to extend along one side of the slot 35, and the spacing between these pipes and the recovery pipes 20 is such that the latter extend along the opposite side of the slot. The respective discharge and recovery openings in the two series of pipes face each other across and slightly above the upper end of the slot so that the air flow therebetween completely bridges the latter. In operation, the pressure of the air delivered by the fan 10 is of a value such that the velocity of the air flowing across the slot precludes any particles of dirt, scale and other foreign matter from passing therethrough into the furnace chamber. The air curtain thereby effectively seals the slot. It will be noted that the drop rods are completely free of any engagement with the slot-defining or other portions of the furnace roof and, therefore, are not in any way restrained from moving in the slot.

Although the duct arrangement described above comprises parallel rows of discharge and recovery pipes, thus suiting it for use in sealing a straight section of a furnace roof slot, it will be obvious that the same air seal may be had with curved slot sections merely by conforming the supply and recovery pipes to the slot shape. The advantages of this seal may, therefore, be realized with U- shaped enameling furnaces as well as those of the straightthrough type and the seal readily provided over the entire extent of the slot. considerable extent, a plurality of duct systems of the nature shown in Fig. 1 may be used side-by-side to handle successive longitudinal sections of the furnace. It will also be apparent that the air collected in the recovery system may be suitably filtered before returned to the fan for recirculation.

In the slightly modified construction shown in Fig. 3, the air discharge means is in the form of a square duct 41 attached to the furnace at one side of the slot 42 and having an opening 43 along its lower corner adjacent the slot. A bafiie plate 44 is welded at the upper edge of this opening to extend outwardly toward the slot and thus confine the air flow to a thin stream directed across the upper slot end substantially at the surface thereof. In this system, in which the air is supplied the duct 41 through several conduits, one being shown at 45, connected to the fan outlet, the discharged air is not recirculated. In order to break up the air blast, a bafiie member comprising a vertical wall 46 and an inwardly directed upper flange 47 is attached at the opposite side of the slot so that the air will impinge thereagainst.

The resultant air curtain is similar to that obtained with the first described system but here the fan continuously supplies fresh air. The discharge pipe or duct of this form of the invention may be continuous or made up of In a straight-through furnace of l several closely spaced individual lengths as in the case of the pipes 17 of the Fig. 1 system, and the modified construction clearly may be used in the same manner with respect to adaptability to varying types of furnaces. The slot of Fig. 3 dilfers somewhat in that vertical refractory tiles 48 define the same with slot castings 49 protecting the tops and upper edges of such tile. The roof itself is again made up of refractory blocks 50 and the conveyor mechanism is as previously described.

Both forms of the invention then clearly seal a furnace roof slot without any need for mechanical bridging mem bers, such as shoe plates, which themselves constitute possible sources of foreign matter falling through the slot onto the ware being processed. This air seal obviously simplifies the work supporting and conveying mechanism, since the same is not required to carry any sliding seal elements and performs only its primary function of moving the work through the furnace. As already noted, an air seal of this nature may be employed without regard to the specific form or shape of the furnace.

In both invention forms, the blast of sealing air is broken up immediately after crossing the slot to prevent the same from continuing out over the furnace roof into the room and to create a turbulence suflicient to destroy any Venturi effect which would draw furnace air out the slot. The recovery pipes of the Fig. 1 construction, of course, trap most of the discharged air but a portion thereof impinges against the sides of the pipes and this air is confined, particularly by the baflle plates 22, so that turbulence is produced. Likewise, the flange 47 of the Fig. 3 baffle plate confines the air impinging against the latter, causing considerable turbulence, and, moreover, the bot! tom location of the duct opening 43 reduces the likelihood of Venturi action by causing the air to flow substantially at the slot surface.

While my invention has been described in detail as applied to the sealing of a roof slot, it will be evident that it may be similarly used to seal a slot in the bottom of a furnace. An example of a furnace having a slotted bottom wall, as contrasted to a slotted roof, appears in my Patent No. 2,608,740, granted September 2, 1952, and the construction there disclosed comprises a continuous articulated shield closing the slot in much the same manner as the shoe plates discussed in the foregoing. A furnace of this further type could obviously be equipped with air seal means of the nature disclosed herein in lieu of such a bottom shield, and this air seal would effectively prevent dust-bearing convection currents rising from the conveyor pit from entering the furnace.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In combination with a furnace having a slotted roof, an overhead track, drop rods mounted for movement along said track in spaced apart relation and extending downwardly through the roof slot to support work in the furnace chamber, the drop rods being mounted completely free of any engagement with the furnace roof so as to move in the slot without restraint, air supply pipe means ailixed to the furnace roof at one side of the slot having an elongated blast orifice extending in the direction of and facing across the slot, blower means for supplying air under pressure to said pipe means, the supply pressure being sufficient so that the air discharged from the blast orifice flows across the slot at a rate which precludes the passage therethrough of dirt, scale and the like, and battle means at the opposite side of the slot in the path of discharge air flow for breaking up the same.

2. In a furnace having a longitudinally extending slot through which externally mounted workssupporting members project, means for flowing air at high velocity across the outer end of such slot over substantially the entire length of the latter, and means disposed in the air path at the side of the slot opposite that at which such air is discharged so that the air will impinge thereagainst and the flow thus be broken up.

3. In a furnace having a longitudinally extending slot through which externally mounted work-supporting members project, an elongated conduit arranged closely adjacent the outer end of such slot to one side thereof, a relatively narrow discharge opening extending substantially the length of the slot and positioned to discharge air supplied under pressure to the conduit in the form of a thin curtain flowing across the surfaces of the respective outer edge-defining members of the slot, a bafiie located at the other slot side in the path of discharge air flow, and blower means for supplying air to said conduit at a pressure such that the velocity of the resulting air curtain precludes the passage of dirt and the like therethrough.

4. In a furnace having a slotted roof and spaced work supporting members mounted on an overhead track to project through the roof slot into the furnace chamber, means for sealing such slot against the entrance of dirt, scale and the like while permitting the work-supporting members to move freely therein, said means comprising a series of elongated air conduits supported in end-to-end relation on the furnace roof to one side of the upper slot end, each such conduit having a relatively narrow longitudinal discharge opening extending substantially the length thereof in its side portion facing the slot, said conduits being adapted to discharge air supplied thereto under pressure across the upper slot end with the combined flow from the several conduits forming a substantially continuous air curtain over the length of the slot, a fan for thus supplying air to said conduits, an air distributing system connecting the conduits commonly to said fan, individual flow control means operatively associated with each conduit for regulating the supply of air thereto and means disposed in the air path at the side of the slot opposite that at which air is discharged so that the air will impinge thereagainst and the flow thus be broken up.

References Cited in the file of this patent UNITED STATES PATENTS 1,725,059 Colby Aug. 20, 1929 1,725,129 Carpenter et a1. Aug. 20, 1929 2,430,191 Schrumn Nov. 4, 1947 2,500,606 Dasmar Mar. 14, 1950 2,516,432 Spencer July 25, 1950 FOREIGN PATENTS 848,691 France July 31, 1939 

